The use of radar and particularly pulsed radar systems for range and angle tracking of target objects have proved heretofore to be the best means of tracking enemy objects. Such pulsed radar systems, however, are vulnerable to electronic countermeasures (ECM) of enemy repeater radars which foils own radar system. The transmission of pulses from own radar to range upon or angle track an enemy object carrying a repeater countermeasure radar system enables the enemy radar to pick up each transmitted pulse and send it back to own radar at high power to cause the tracking gates of own radar to follow this higher power false echo pulse. The enemy repeater radar system thereafter produces a progressively increasing delay in the repeated pulses which causes the range tracking gate of own radar to be pulled away from the actual target and on to a decoy signal. Consequently, own radar is caused to track a false signal which will produce a target indication far removed from the actual target whereupon own radar becomes useless in tracking the enemy object. Anti-jam circuits therefore become essential to a range and angle tracking radar system to guard against the deceptive repeated jamming signals of an ECM repeater radar system.
In the present invention it is recognized that two things must be accomplished to nullify the effects of ECM radar equipment:
First, the system must remove the power advantage of the jamming signal compared to the target echo signal, and
Second, the system must provide a cancellation signal of duration at least equal to the system pulse width and of amplitude at least equal to the reduced jamming signal. The cancellation signal must occur in time immediately following the trailing edge of the true target echo signal.